A conventional window wall or curtain wall system 100 is shown in FIG. 1. Typically such conventional window wall or curtain wall systems include a plurality of support mullions 102 oriented generally along horizontal and vertical lines. The mullions, when connected one to another provide a structure for supporting substantially rigid wall or window panels 104. Each supported, substantially rigid wall or window panel typically has a rectangular shape characterized by two sets of parallel edges. Such window wall or curtain wall systems may include just a single wall or window panel or multiple wall or window panels as shown in FIG. 1. Window wall or curtain wall systems have been used both in interior spaces and as external walls in buildings. Additionally, window wall or curtain wall systems 100 have been used in vehicles such as buses, airplanes, trains, or boats.
Shown in FIG. 2 is a simplified example of a system 200 for connecting a horizontal mullion 202 to a vertical mullion 204. While the mullions shown in FIG. 2 are simple box beams, most present day mullions used in window wall or curtain wall systems are usually complex extruded forms. In the exemplary diagram shown in FIG. 2, the shear block 206 is attached to the vertical mullion 204 using fasteners 208. The fasteners 208 typically enter the mullion at an angle which is substantially perpendicular to an exterior surface of the mullion. Once the shear block 206 is attached to the mullion 204, the substantially hollow horizontal mullion 202 is then slid over the shear block 206.
FIG. 3 illustrates two types of shear blocks 302, 304 used in actual practice. As shown in FIG. 2, fasteners 306, which typically pass through the shear blocks at an angle which is substantially perpendicular to the exterior surface of the mullion block, are used to attach the shear blocks shown in FIG. 3 to the vertical mullion 308.
In window wall or curtain wall installations employing mullions with more complex non-orthogonal shapes, because of either construction or aesthetic considerations, it is necessary to use a shear block having a more complex shape to both fit within the mullion and to assure that the fasteners pass into the mullion at an angle which is substantially perpendicular to an exterior surface. For example, in the system 400 illustrated in FIG. 4, a specially manufactured diamond-shaped vertical mullion 402 is used instead of the box beam 204 shown in FIG. 2. Because of the use of a diamond-shaped mullion 402, the shear block 404 must be formed such that a top and bottom plan view of the shear block 404 would have the shape of a non-rectangular parallelogram having two short minor edges 406 and two longer major edges 408. The use of a non-rectangular parallelogram enables the compound fastening of non-orthogonal surfaces. Additionally, the fastener holes 410 must be re-oriented in the shear block 404 so that their long axis is substantially perpendicular to the external surface of the mullion. This assures proper attachment of the shear block 410 to the mullion 402. Typically, prior art specially created shear blocks 404 enable the use of non-orthogonal mullions in custom window wall or curtain wall installations and are specially produced in small volumes by making special molds or castings. If the specially designed and specially manufactured shear block further requires the inclusion of channels, ears, fingers, legs, spines, etc., as shown in shear blocks 302 and 304 in FIG. 3, to accommodate and properly orient fasteners with respect to the outer surface of the mullion, the design and manufacture of such specially made shear blocks is expensive. And, because such specially designed and specially made shear blocks are produced in relatively small quantities, their unit cost is high. As the design of specially made shear blocks depends on the shape of the mullions and the design of the particular window wall or curtain wall system, unused specially designed shear blocks have little use on other installations and are usually discarded as scrap.
As the complexity of shear block design increases with the complexity of the design of window wall or curtain wall systems, so too does the chance for error when designing and manufacturing the required specially made shear blocks. There is therefore a need in the art to create a shear block system for use in connecting mullions, one to another, that is inexpensive, easy to manufacture and reduces the possibility for errors or rework.